The miniaturisation of chemical processes onto chip-based platforms enables a plethora of novel industrial applications of existing and new chemistry, biochemistry, biomolecular science and particle science in both analysis, synthesis, assembly, decision making and computing. For example, molecular synthesis in micron-scale reactors benefits from (i) fast reaction kinetics, and (ii) high specific-areas which facilitates greater control of and/or the use of highly exothermic reactions. Many advances in so-called, microfluidics have been made in recent years. Nevertheless, known devices and methods for the manipulation of fluids in miniaturised tubes, ducts and vessels have not met all the requirements of industry. For example, sterilisation of, and the maintenance of an inert atmosphere in, microfluidic ducts remains a problem hampered by the materials from which many devices have been constructed. Additionally, the use of highly corrosive fluids and high temperatures again requires very strict attention to the materials from which devices are fabricated, which, in turn, has serious implication for mass-manufacture of such devices and assemblies of such. Accordingly, special attention must be made to the suitability of constructional materials, the unit costs of manufacture, the rapidity of manufacture, including tooling time for mass-production, and the translation of prototyping methods to mass-production. Constructional materials may include a glass, ceramics, stainless steel and other metals or alloys, silicon, polymers, paper and others. Glass-based substrates have been successfully manufactured, but limited, to some extent, by the complexity of 3-dimensional geometry that is cost-effectively feasible. Also, external fluidic interconnect solutions remain crude. Photostructurable glasses (e.g. Fotoran made by Schoot) are very expensive, sometimes 200× the cost of polymer substrates, and require several expensive and hazardous processing steps (e.g. use of HF) and specialised equipment (e.g. quartz based optics for lithography). Stainless steel chips can be manufactured but are limited with respect to 3-dimensional geometries attainable and the surface quality possible, even with MicroElectroDischarge Machining, is frequently of insufficient resolution for microfluidic applications. The technique suffers from high unit-cost production and very limited availability of high resolution machining tools. Silicon based microfluidic devices, such as microreactors, have been made and benefit from available tools for silicon micromachining and fusion/anodic bonding procedures for bonding together multilayered devices. However, silicon is relatively expensive for mass fabrication of relatively large-format chips which may sometimes have a short-lifespan. In addition, with exceptions, interconnect solutions remain inelegant and low-pressure and silicon denies the use of high field strength electric fields for the generation of electro-kinetic flow and certain molecular purification processes.
Many polymers (e.g. polysulphone, polycarbonate, polymethylmethacrylate) have been utilized for the fabrication of microreactors but most have been unsuitable for use with very aggressive liquids such as acids (e.g. nitric acid) and solvents (e.g. acetonitrile). In addition, the presence of certain substances incorporated into the polymer matrix, such as plasticisers, may cause contamination during usage, as those compounds leach from the substrate matrix into the fluids within the ducts on the chip. Particularly, for many synthetic reactions the preferred substrate material would be a fluoropolymer such as polytetrafluoroethylene (C2F4)n [PTFE]. However PTFE and related variants are less easily micromachined to provide fluidic ducts of micron sized dimensions and very difficult to join with itself to form enclosed microreactor ducts. It is a purpose of the current invention disclosed herein to provide a cost-effective resolution to the latter technical problems and enable the manufacture of suitable chip-based platforms for a wide range of industrial-scale diagnostic and synthesis operations.
Additionally, fluid flow in microscale ducts is characterised by laminar flow conditions resulting from characteristically low Reynolds number regimes. This causes a problem with mixing of fluids and it is a purpose of the invention disclosed herein to provide a solution to that technically limiting issue. Also, fluid flow in micron scale ducts is usually characterised by continuous streams of a given fluid phase. A contrasting method is where immiscible phase fluids are caused to flow along a duct in serial discontinuous aliquots. The generation of such segmented flow streams can be enabled by bringing together two streams of immiscible fluid and causing them to merge at a so-called T-junction. This methodology has not met all the needs of industry. For example, such device configurations are frequently only stable for a narrow range of absolute flow rate conditions and relative flow rates of the immiscible phase liquids. In particular, it can be difficult to control the generation of segmented flow streams with equal volumes of the immiscible phases, especially at low flow rates required by many applications. In addition, back-pressure can be considerable, especially in ducts of narrow (<100 microns width, depth, both or diameter) and very narrow (<25 micron width, depth, both or diameter) dimensions. It is, therefore, a purpose of the invention disclosed herein, to provide improved solutions for the generation and subsequent manipulation of segmented flow streams in micron scale ducts.
Devices for the manipulation of fluids may be used for analytical and synthesis purposes. Frequently, for a wide range of functional operations in both analytical and synthesis techniques it is necessary to elute precise volumes of fluids in a highly repeatable manner. For example, in titrations, ‘split and mix’ procedures, formation of microparticles such as artificial cells and nanoparticles such as quantum dots. Because the volumes of liquids are usually very small it is frequently difficult to meet the exacting requirements of industry and solutions to date are generally insufficient to meet all needs. It is a further purpose of the invention disclosed herein to provide device configurations and methods to improve substantially on those currently available. Furthermore, notwithstanding that devices and methods currently available for the controlled volumemetric elution of liquids, do not meet current needs, the subsequent manipulation of small liquid volumes also requires improvements. In particular, there is a need to improve on techniques for altering the morphology of liquid samples, their conversion to non-liquid forms and the ability to encapsulate such small samples with films of other materials. It is also a further purpose of the invention disclosed herein to provide further devices and associated methods to meet these needs.